Is there any difference in the way the TXINHIBIT signal works in the Virtex-II Pro, Virtex-II Pro X, and Virtex-4 MGTs?
In Virtex-II Pro, the TXINHIBIT signal, goes directly from the TXUSRCLK2 domain to the REFCLK domain.
TXUSRCLK does not have to be stable for TXINHIBIT to work. The TXINHIBIT has priority over TXRESET.
In Virtex-II Pro X, the TXINHIBIT signal is synchronous only to REFCLK. It is not affected by USRCLK or USRCLK2.
TXRESET has priority over the TXINHIBIT signal with respect to how it affects the data transmitted out of the PMA.
In Virtex-4, the TXINHIBIT signal is asynchronous. The TXINHIBIT has priority over TXRESET.
For more information, refer to (Xilinx Answer 21305).